U.S. patent application number 10/928511 was filed with the patent office on 2005-02-03 for golf club head.
This patent application is currently assigned to Taylor Made Golf Company, Inc.. Invention is credited to Burnett, Michael Scott, Hoffman, Joseph H., Willett, Kraig A..
Application Number | 20050026720 10/928511 |
Document ID | / |
Family ID | 25410116 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050026720 |
Kind Code |
A1 |
Willett, Kraig A. ; et
al. |
February 3, 2005 |
Golf club head
Abstract
A golf club head is provided having a substantially increased
sweet spot across its striking face. A preferred embodiment
includes a striking plate with a substantially annular area on a
rear surface that has an increased thickness or stiffness
surrounding the central region of the balance point of the striking
surface. The central region of the striking plate has a generally
reduced thickness or stiffness that is less than the maximum
thickness or stiffness values found at the third and fourth
thickness or stiffness profiles of the substantially annular area
but greater than a minimum thickness or stiffness values at the
peripheral area. The first and second thickness or stiffness
profiles of the substantially annular area have thicknesses or
stiffnesses less than the maximum values of the third and fourth
thickness or stiffness profiles but more than the minimum thickness
or stiffness values at the periphery.
Inventors: |
Willett, Kraig A.;
(Fallbrook, CA) ; Hoffman, Joseph H.; (Carlsbad,
CA) ; Burnett, Michael Scott; (Carlsbad, CA) |
Correspondence
Address: |
SHEPPARD, MULLIN, RICHTER & HAMPTON LLP
333 SOUTH HOPE STREET
48TH FLOOR
LOS ANGELES
CA
90071-1448
US
|
Assignee: |
Taylor Made Golf Company,
Inc.
|
Family ID: |
25410116 |
Appl. No.: |
10/928511 |
Filed: |
August 27, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10928511 |
Aug 27, 2004 |
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10302331 |
Nov 22, 2002 |
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6800038 |
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10302331 |
Nov 22, 2002 |
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09898843 |
Jul 3, 2001 |
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6824475 |
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Current U.S.
Class: |
473/342 |
Current CPC
Class: |
A63B 53/0408 20200801;
A63B 53/0412 20200801; A63B 53/0416 20200801; A63B 60/00 20151001;
A63B 53/0466 20130101; A63B 53/0458 20200801; A63B 53/04
20130101 |
Class at
Publication: |
473/342 |
International
Class: |
A63B 053/04 |
Claims
We claim:
1. A golf club head, having a coefficient of restitution measuring
at least about 0.80, comprising: a body having a toe portion, a
heel portion, a sole portion, and a crown portion, together
defining a front opening; a striking plate disposed at the opening,
the striking plate having a substantially planar striking surface
on a front side, a rear surface on a rear side, and a periphery for
attachment at the opening on the body; wherein the periphery has a
top edge, a bottom edge, a first side edge, and a second side edge,
and each point on the striking plate has a thickness; wherein the
striking surface has a balance point at a central region and
further has a total area on its front side; wherein the striking
plate has a first thickness profile between the balance point and
the top edge, a second thickness profile between the balance point
and the bottom edge, a third thickness profile between the balance
point and the first side edge, and a fourth thickness profile
between the balance point and the second side edge; wherein the
first, second, third, and fourth thickness profiles have thickness
values at first locations encompassing the periphery of the
striking plate and include minimum values adjacent the edges;
wherein the first, second, third, and fourth thickness profiles
have thickness values at second locations positioned between the
first locations and the balance point, and third locations
positioned in the central region between the second locations and
the balance point; wherein the third and fourth thickness profiles
having thickness values at least 1.5 times the minimum values at
the second locations and include points having maximum values;
wherein the first and second thickness profiles having thickness
values at the second locations that are less than the maximum
values of the third and fourth thickness profiles at the second
locations, but greater than the minimum values of the first,
second, third, and fourth thickness profiles at the first
locations; and wherein the first, second, third, and fourth
thickness profiles have thickness values at the third locations in
the central region that are less than the maximum values of the
third and fourth thickness profiles at the second locations but
greater than the minimum values of the first, second, third, and
fourth thickness profiles at the first locations.
2. The golf club head of claim 1, wherein the first, second, third,
and fourth thickness profiles in combination represent a
substantially annular region of increased thickness comprising the
second locations
3. The golf club head of claim 1, wherein the coefficient of
restitution of the head is greater than 0.80
4. The golf club head of claim 1, wherein the first and second
thickness profiles have thickness value at the second locations
that are substantially equal to the minimum thickness values of the
first, second, third, and fourth thickness profiles at the first
locations.
5. The golf club head of claim 1, wherein the body is a hollow
cavity closed by the striking plate
6. The golf club head of claim 1, wherein the body at least
partially comprises at least one type of metal or alloy
material.
7. The golf club head of claim 1, wherein the striking plate
comprises at least one type of metal or alloy material.
8. The golf club head of claim 1, wherein the striking plate at
least partially comprises a composite material.
9. The golf club head of claim 1, wherein the body at least
partially comprises a composite material.
10. A striking plate for a golf club head, comprising: a striking
plate having a substantially planar striking surface on a front
side, a rear surface on a rear side and a periphery for attachment
to the golf club head, the periphery having a top edge, a bottom
edge, a first side edge and a second side edge; the striking
surface having a balance point at a central region of the striking
plate and each point on the striking surface having a local
cross-sectional bending stiffness profile, the striking surface
having a total area on the front side of the striking plate; the
striking plate having a first stiffness profile between the balance
point and the top edge, a second stiffness profile between the
balance point and the bottom edge, a third stiffness profile
between the balance point and the first side edge and a fourth
stiffness profile between the balance point and the second side
edge; the first, second, third, and fourth stiffness profiles
having stiffness values at first locations encompassing the
periphery of the striking surface and including minimum values
adjacent the periphery; the third and fourth stiffness profiles
having stiffness values at least 3.5 times the minimum values at
the second locations and including points having maximum values;
the first and second stiffness profiles having stiffness values at
the second locations that are less than the maximum values of the
third and fourth stiffness profiles at the second locations, but
greater than the minimum values of the first, second, third, and
fourth stiffness profiles at the first locations; and the first,
second, third, and fourth stiffness profiles having stiffness
values at the third locations in the central region that are less
than the maximum values of the third and fourth stiffness profiles
at the second locations but greater than the minimum values of the
first, second, third, and fourth stiffness profiles at the first
locations.
11. The striking plate of claim 10, wherein the first, second,
third, and fourth stiffness profiles in combination represent a
substantially annular region of high stiffness comprising the
second locations.
12. The striking plate of claim 11, comprising a first surface of
substantially constant thickness having the striking surface formed
thereon and a second surface of varying thickness forming the rear
surface of the striking plate.
13. The striking plate of claim 12, wherein the first and second
surfaces of the striking plate are separately formed and fixedly
attached together.
14. The striking plate of claim 12, wherein the first and second
surfaces of the striking plate are integrally formed.
15. The striking plate of claim 10, wherein the coefficient of
restitution of the striking plate is greater than 0.80.
16. The striking plate of claim 10, wherein the first and second
thickness profiles have thickness value at the second locations
that are substantially equal to the minimum thickness values of the
first, second, third, and fourth thickness profiles at the first
locations.
17. The striking plate of claim 10, wherein the striking plate
closes hollow cavity of the golf club head.
18. The striking plate of claim 10, wherein the striking plate at
least partially comprises at least one type of metal or alloy
material.
19. The striking plate of claim 10, wherein the striking plate at
least partially comprises a composite material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of application Ser. No. 10/302,331,
filed Nov. 22, 2002, which is a continuation-in-part of application
Ser. No. 09/898,843, filed Jul. 3, 2001, both of which are herein
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to golf club heads
and, more particularly, to golf club heads having an improved face
construction.
[0003] Modem golf clubs have typically been classified as woods,
irons or putters. Additionally, a newer class of golf clubs termed
"utility" clubs or "iron woods" seek to replace low lofted long
irons or higher numbered fairway woods. The term "wood" is a
historical term that is still commonly used, even for golf clubs
that are constructed of steel, titanium, fiberglass and other more
exotic materials, to name a few. The woods are now often referred
to as "metal woods." The term "iron" is also an historical term
that is still commonly used, even though those clubs are not
typically constructed of iron, but are rather constructed of many
of the same materials used to construct "woods".
[0004] One particular improvement that relates especially to metal
woods is the use of lighter and stronger metals, such as titanium.
A significant number of the premium metal woods, especially
drivers, are now constructed primarily using titanium. The use of
titanium and other lightweight, strong metals has made it possible
to create metal woods of ever increasing sizes. The size of metal
woods, especially drivers, is often referred to in terms of volume.
For instance, current drivers may have a volume of 300 cubic
centimeters (cc) or more. Oversized metal woods generally provide a
larger sweet spot and a higher inertia, which provides greater
forgiveness than a golf club having a conventional head size.
[0005] One advantage derived from the use of lighter and stronger
metals is the ability to make thinner walls, including the striking
face and all other walls of the metal wood club. This allows
designers more leeway in the positioning of weights. For instance,
to promote forgiveness, designers may move the weight to the
periphery of the metal wood head and backwards from the face. As
mentioned above, such weighting generally results in a higher
inertia, which results in less twisting due to off-center hits.
[0006] There are limitations on how large a golf club head can be
manufactured, which is a function of several parameters, including
the material, the weight of the club head, the strength of the club
head, and the materials used. Additionally, to avoid increasing
weight, as the head becomes larger, the thickness of the walls must
be made thinner, including that of the striking face. As a result,
as the striking face becomes thinner, it has a tendency to deflect
more and more at impact, and thereby has the potential to impart
more energy to the ball. This phenomenon is generally referred to
as the "trampoline effect." A properly constructed club having a
thin face can therefore impart a higher initial velocity to a golf
ball than can a club having a rigid thick face. Because initial
velocity is an important factor in determining how far a golf ball
travels, this is very important to golfers.
[0007] It is appreciated by those skilled in the art that the
initial velocity imparted to a golf ball by a thin-faced metal wood
varies depending on the location of the point of impact of a golf
ball on the striking face. Generally, balls struck in the sweet
spot will have a higher rebound velocity. Many factors contribute
to the location of the sweet spot, including the location of the
center of gravity (CG) and the shape and thickness of the striking
face.
[0008] Prior golf club heads have provided an increased initial or
launch velocity of a golf ball, by incorporating a lightweight,
flexible face. Manufacturers of metal wood golf club heads have
more recently attempted to manipulate the performance of their club
heads by designing what is generically termed a variable face
thickness profile for the striking face, in particular with the use
of lightweight materials such as titanium alloys.
[0009] Another approach to reduce stress at impact is to use one or
more ribs extending substantially from the crown to the sole
vertically across the face, and in some instances also extending
from the toe to the heel horizontally across the face. Because the
largest stresses are located at the impact point, usually at or
substantially near the sweet spot, the center of the face is also
thickened and is at least as thick as the ribbed portions.
[0010] There have been other configurations and ribs formed on the
back of a club face, including one or more thin rings, a power bar,
and a cone formation. Multiple thin rings have been attached by
various means so as to add mass directly behind the sweet spot, and
alternatively a spiral formation has been used, wherein the
multiple rings or spiral mass extend from the sweet spot
substantially toward the periphery of the face plate. A single thin
ring at the sweet spot has been used on an iron club head in
conjunction with an added toe mass in order to reposition a point
of least rigidity to the center of the face. In this configuration
the rigidity of the face is always higher radially outward from the
centered ring.
[0011] Other club heads have attempted to utilize power bars or
cones behind the sweet spot in order to increase the force imparted
to a golf ball. These power bars and cones involve significant
additional mass extending toward a rear of the club head, thus
affecting the club head's center of gravity. However, such club
heads do not provide a coefficient of restitution (COR) that is at
least the minimum value of approximately 0.8 that is sought by
today's golfers.
[0012] The COR for a golf club may be informally defined as a
function of the ratio of the relative velocities of a golf ball,
just prior to and immediately after impact with the golf club head.
The COR baseline value of e=0.822 has been established in the
United States, and the formal equation also accounts for the
relative masses of a specific club head as well as a golf ball, as
follows:
V.sub.out/V.sub.in=(eM-m)/(M+m)
[0013] (where M is the mass of the club head and m is an average
mass of the golf ball population. V.sub.out is the ball rebound
velocity and V.sub.in is the incoming velocity of the ball that is
shot at the face of the golf club head using an air cannon, for
example.)
[0014] In each of the foregoing examples, however, there is
ultimately a failure to provide significant forgiveness to
off-center hits. Each golf club has attempted to increase COR while
addressing to various degrees the difficulties in doing so. For
these clubs, the point of impact must still be at the sweet spot in
order for these clubs to deliver their highest COR, and even the
slightest deviation of the impact from the sweet spot will result
in a significant loss in ball velocity.
SUMMARY OF THE INVENTION
[0015] The present invention provides a solution to enable club
designers to overcome the problems described above, including a
golf club head that exhibits greater forgiveness across a
substantial portion of the striking face while continuing to impart
high initial velocity to a golf ball.
[0016] In a preferred embodiment of the invention, a golf club head
having a coefficient of restitution measuring at least about 0.8 is
provided. The club head has a body having a toe portion, a heel
portion, a sole portion, and a crown portion, together defining a
front opening. A face insert is disposed in the opening and has a
substantially planar striking surface on a first side, a rear
surface on a second side, and a periphery for attachment at the
opening on the body. This periphery has a top edge, a bottom edge,
a first side edge, and a second side edge. The striking surface has
a balance point at a central region of the insert, each point on
the striking surface has a thickness.
[0017] The face insert has a first thickness profile between the
balance point and the top edge, a second thickness profile between
the balance point and the bottom edge, a third thickness profile
between the balance point and the first side edge, and a fourth
thickness profile between the balance point and the second side
edge. The first, second, third, and fourth thickness profiles
similarly have thickness values at first locations encompassing the
periphery of the striking surface and including minimum values
adjacent the edges. The thickness profiles similarly have thickness
values at least 1.5 times the minimum values at second locations
between the first locations and the balance point, and the second
locations include points having maximum thickness values. The
thickness profiles similarly have thickness values at third
locations in the central region that are less than the maximum
values at the second locations, but greater than the minimum values
at the first locations.
[0018] The first, second, third, and fourth thickness profiles, in
combination, represent a substantially annular region of increased
thickness comprising the second locations. The thickness values of
the third locations form a reduced thickness region, and an area
including the substantially annular region and the reduced
thickness region extend about 50% of the distance from the balance
point to each of the top and bottom edges and the first and second
side edges.
[0019] Alternatively, a golf club head of the present invention may
comprise a body defining a toe portion, a heel portion, a sole
portion, a crown portion, and a face portion. The face portion has
a striking surface on an outer side and a periphery substantially
adjacent a first junction at the face and crown portions, a second
junction at the face and sole portions, a third junction at the
face and toe portions, and a fourth junction at the face and heel
portions. The striking surface has a total area as measured on its
outer side, and it has a balance point at a central region of the
face portion.
[0020] Each point on the striking surface has a local
cross-sectional bending stiffness such that the face portion has a
first stiffness profile between the balance point and the first
junction and a second stiffness profile between the balance point
and the third junction. The first and second stiffness profiles
similarly have low first stiffness values at first locations that
are farthest from the balance point and that encompass the
periphery of the striking face. The first and second stiffness
profiles similarly have high second stiffness values at second
locations that are between the periphery and the balance point, and
the first and second stiffness profiles similarly have third
stiffness values at the central region.
[0021] The face portion is substantially symmetric about central
vertical and horizontal axes such that the first stiffness profile
also applies between the balance point and the second junction, and
the second stiffness profile applies between the balance point and
the fourth junction. The first stiffness values include minimum
values adjacent the first, second, third, and fourth junctions,
with the first stiffness values increasing to less than about 3.4
times the minimum values. The second stiffness values are at least
about 3.5 times the minimum values, and the third stiffness values
are greater than the minimum values and less than about 3.5 times
the minimum values. The second and third stiffness values comprise
an area of the striking surface that extends approximately halfway
from the balance point to the first, second, third, and fourth
junctions.
[0022] In another embodiment of the present invention, a face
insert for a golf club head comprises a substantially planar
striking surface on a first side of the insert, a rear surface on a
second side, and a periphery for attachment to the golf club head.
The periphery has a top edge, a bottom edge, a first side edge, and
a second side edge. The striking surface has a balance point at a
central region of the face insert, and each point on the striking
surface has a local cross-sectional bending stiffness. The striking
surface has a total area on the first side of the insert.
[0023] The face insert has a first stiffness profile between the
balance point and the top edge, a second stiffness profile between
the balance point and the bottom edge, a third stiffness profile
between the balance point and the first side edge and a fourth
stiffness profile between the balance point and the second side
edge. The first, second, third, and fourth stiffness profiles have
stiffness values at first locations that encompass the periphery of
the striking face and include minimum values adjacent the edges.
The stiffness profiles have stiffness values at second locations
between the first locations and the balance point that are at least
3.5 times the minimum values which are generally located at the
periphery. The second locations include points having maximum
stiffness values, and the stiffness profiles have stiffness values
at third locations in the central region that are less than the
values at the second locations but greater than the minimum values
at the first locations.
[0024] The first, second, third, and fourth stiffness profiles in
combination represent a substantially annular region of high
stiffness comprising the second locations. The stiffness values of
the third locations form a reduced stiffness region including a
point having a local minimum stiffness value. The substantially
annular region comprises at least about 12% of the total area of
the striking surface.
[0025] In yet another embodiment of the invention, the striking
plate has a first thickness profile between the balance point and
the top edge, a second thickness profile between the balance point
and the bottom edge, a third thickness profile between the balance
point and the first side edge, and a fourth thickness profile
between the balance point and the second side edge. The first,
second, third, and fourth thickness profiles have similar thickness
values at first locations encompassing the periphery of the
striking surface and have minimum values adjacent the edges. The
third and fourth thickness profiles have thickness values that are
at least 1.5 times the minimum values and include points with the
maximum values at the second locations. The first and second
thickness profiles have thickness values at second locations that
are less than the maximum values of the third and fourth thickness
profiles at the second locations, but greater than minimum values
of the first, second, third, and fourth thickness profiles at the
first locations. The first, second, third, and fourth thickness
profiles have thickness values at third locations, in the central
region of the face insert, that are less than the maximum values of
the third and fourth thickness profiles at the second locations,
but greater than the minimum values of the first, second, third,
and fourth thickness profiles at the first locations.
[0026] Generally, the present invention can be practiced using a
variety of common club head shapes that are known in the art.
According to another preferred embodiment of the invention, a
hollow metallic body is disclosed. The body has a plurality of thin
walls including a toe portion, a heel portion, a sole portion, and
a crown portion, wherein all of such portions cooperate to define
an interior cavity and to define an opening with a forward edge. A
metallic ball striking face insert is secured to the front edge of
the body, using methods that are generally known in the art. This
embodiment has a ball striking face insert with substantially
uniform wall thickness, as measured from the striking surface to
the rear surface, except for a portion of the face insert near the
center. Near the center of the face insert, there is an oblong,
washer-shaped region of increased thickness that extends rearwardly
into the cavity. The washer-shaped region is preferably formed as
an integral part of the rear surface of the face insert, although
the washer-shaped region may be fixedly attached to the rear of the
insert through means known in the art. The washer-shaped region
serves to lessen the relative amount of flex in the face insert and
results in a club head that is more forgiving of off-center hits
than that of a similar-sized face having a uniform thickness
profile. Generally, the region of increased thickness is located
radially outward from the sweet spot.
[0027] The present invention provides a solution to enable club
designers to overcome the problems described above, including a
golf club head that exhibits greater forgiveness across a
substantial portion of the striking surface while continuing to
impart high initial velocity to a golf ball.
[0028] Other features and advantages of the present invention
should become apparent from the following description of the
preferred embodiments, taken in conjunction with the accompanying
drawings, which illustrate, by way of example, the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 shows a front view of a first embodiment of a golf
club head of the present invention.
[0030] FIG. 2 is a cross-sectional view of the golf club head of
FIG. 1, taken along lines 2-2 in FIG. 1.
[0031] FIG. 3 is a cross-sectional view of the golf club head of
FIG. 1, taken along lines 3-3 in FIG. 1.
[0032] FIG. 4 is a rear elevational view of a face insert
corresponding to the golf club head of FIG. 1.
[0033] FIG. 5 is a rear elevational view of a forged face insert in
a second embodiment of the present invention.
[0034] FIG. 5A is a cross-sectional view of the forged face insert
of FIG. 5, taken along lines A-A in FIG. 5.
[0035] FIG. 5B is a cross-sectional view of the forged face insert
of FIG. 5, taken along lines B-B in FIG. 5.
[0036] FIG. 6 is a rear elevational view of a machined face insert
in another embodiment of the present invention.
[0037] FIG. 7 is a cross-sectional view of the machined face insert
of FIG. 6, taken along lines 7-7 in FIG. 6.
[0038] FIG. 8 is a cross-sectional view of the machined face insert
of FIG. 6, taken along lines 8-8 in FIG. 6.
[0039] FIG. 9 is a graph showing the stiffness profile of the
forged face insert of FIG. 5, from the face's balance point (BP) to
a peripheral point (P).
[0040] FIG. 10 is a graph showing the two stiffness profiles of the
forged face insert of FIG. 5, extending from a balance point and
including a local minimum of a central region that is located along
the profile extending toward peripheral points P1 and P2.
[0041] FIG. 11 is a rear elevational view of another embodiment of
a face insert of the present invention that has discontinuous
thicknesses and that is also asymmetric, at least as viewed along a
line between the heel and toe ends of the insert.
[0042] FIG. 12 is a cross-sectional view of the face insert of FIG.
11, taken along lines 12-12 in FIG. 11.
[0043] FIG. 13 is a cross-sectional view of the face insert of FIG.
11, taken along lines 13-13 in FIG. 11.
[0044] FIGS. 14 and 14A are front and side views, respectively, of
a rear portion to be inertia welded to a face insert of the present
invention. FIG. 14A is cross-sectional view of FIG. 14, taken along
lines A-A in FIG. 14.
[0045] FIGS. 15 and 15A are front and side views, respectively, of
the rear portion of the rear portion shown in FIGS. 14 and 14A
after recesses have been formed for attachment of the inertia
welding apparatus (not shown). FIG. 15A is a cross-sectional view
of FIG. 15, taken along lines A-A in FIG. 15.
[0046] FIGS. 16 and 16A are rear elevational and cross-sectional
views of the rear portion of FIG. 14, with final thicknesses.
[0047] FIG. 17 is a perspective view of another alternative
embodiment of a golf club head in accordance with the
invention.
[0048] FIG. 18 is a is a detailed cross-sectional view of the
striking plate, taken along lines 18-18 of FIG. 17.
[0049] FIG. 19. is a detailed cross-sectional view of the striking
plate, taken along lines 19-19 of FIG. 17, showing the third and
fourth thickness profiles at the second locations with maximum
values.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0050] The drawings depict several preferred embodiments of a golf
club head in accordance with the present invention. With reference
to FIG. 1, a club head 10 is shown that is similar to many metal
wood club heads that are known in the art. Club heads within the
scope of the invention are not necessarily limited to the shape
depicted. The club head comprises a hollow metallic body 11 and a
striking or face plate 20. The body comprises a heel portion 12, a
toe portion 13, a sole portion 14 and a crown portion 16 that
cooperate to define an opening (not shown) that receives the
striking plate. The striking plate is shown in greater detail in
FIGS. 2-4. The club head is normally connected to a shaft (not
shown) by a hosel 17 that is integrally formed with the body.
Preferably, the body is constructed of stainless steel or a
titanium alloy, but alternatively can be constructed of other
materials such as a silicon steel alloy, various composites, and
combinations thereof. The club head is preferably manufactured such
that the body, including the heel portion, toe portion, sole
portion, crown portion and hosel are integrally formed, and the
striking plate having a striking face 15 is fixedly attached by
means known in the art. However, the various portions of the
preferred body may be separately molded, cast, forged or otherwise
manufactured by means known in the art, and fixedly attached to
form the body.
[0051] FIG. 4 shows the rear surface 23 of the striking plate
formed from stainless steel. The rear surface comprises an outer
rear surface 27 and an inner rear surface 29. Between the outer
rear surface and the inner rear surface is a raised surface 28. The
raised surface forms an area that is substantially elliptical.
Proximate the raised surface are an outer shoulder 25 and an inner
shoulder 26 that form a transition between the raised surface and
the outer rear surface and the inner rear surface. The raised
surface and the shoulders 25 & 26 cooperate to form an
elliptical, washer-shaped projection that extends rearward toward
the inside of the club head cavity.
[0052] An alternative preferred striking plate 30 may be forged as
a unitary structure, as shown in FIG. 5. As indicated by the
topographical lines 31 showing the varying thicknesses (32, 33, 34,
35, 36), forging provides the opportunity to form relatively
complex surfaces in a fairly simple process. In this example, the
thickness ranges from about 1.6 mm near the periphery 37 of the
plate, to about 1.9 mm radially inward from the periphery toward a
balance point at about the center 38 of the striking plate. The
thickness increases to about 2.5 mm further inward, up to a maximum
of about 4.8 mm in a generally elliptical portion 39 surrounding a
2.5 mm thickness region at the balance point 38.
[0053] FIGS. 6-8 are similar to FIGS. 2-4 in that the thickness
variation of the rear of the striking plate 40 of FIGS. 6-8 is more
symmetrical than that shown in FIG. 5. The preferred material used
in the embodiment of FIGS. 6-8 is a titanium alloy. As shown in
FIG. 6 the shape of the generally annular region 41 of increased
thickness is round, while in FIG. 2 the annular region of the
raised surface was more elliptical. In addition, the annular region
shown in FIGS. 7 and 8 is somewhat thicker and more gradual in
slope than the region of maximum thickness of the raised surface
shown in FIGS. 2 and 3, in which much of the raised surface is
substantially flat.
[0054] The embodiments of the face portions represented in FIGS.
2-8 share a characteristic that a substantial increase in thickness
occurs within about 75% of the distance from the center (e.g. 29,
38) toward the peripheral edges of the plates (e.g. 37).
Preferably, the thickness increase occurs within about 50% of the
distance from the center to the periphery. Also, the annular
regions (e.g. 41) comprise thicknesses that are at least 50%
greater than the minimum thickness found at the outermost periphery
(42 in FIGS. 6-8) and cover an area at least about 12% of the total
area of the striking plate 40. Preferably, the annular region 41
covers an area at least about 15%, and most preferably at least
about 20%, of the total area of the striking plate. Tables I and II
summarize areas of inertia welded and forged face embodiments,
respectively, according to fraction of total face area for each
level of thickness shown.
1TABLE I Inertia Weld Thickness (mm) Area (mm{circumflex over (
)}2) Fraction of Face Area 2 1016 0.31 2.5 843 0.26 3 666 0.20 3.5
485 0.15 4 298 0.09 4.5 113 0.03
[0055]
2TABLE II Forged Face Thickness (mm) Area (mm{circumflex over (
)}2) Fraction of Face Area 2.1 1369 0.42 2.6 612 0.19 3.1 477 0.15
3.6 349 0.11 3.1 24 0.01 4.6 121 0.04
[0056] For a given material, a point on the club face can be
considered beam-like in cross-section and its bending stiffness at
a given location on the face can be calculated as a cubed function
of its thickness, h.sup.3. That is, EI=.function.(h.sup.3), where E
is the Young's Modulus and I is the inertia. Thus, if a first point
on the face has a thickness of 2 mm and a second point has a
thickness of 3 mm, then the second point is 1.5 times thicker and
has a stiffness that is 3.375 times that of the first point,
or:
(3 mm).sup.3/(2 mm).sup.3=(1.5).sup.3=3.375
[0057] The stiffness values in the central region of the face
containing the sweet spot are at least higher than the minimum
stiffness found at a peripheral point (P) at the outermost region,
however the maximum stiffness of the face is provided a distance
radially outward from the sweet spot. The central region does
include a locally minimum stiffness value which is still greater
than the lowest stiffness found at the outermost region. Referring
to FIG. 9, the central region extends from BP to C, while the
region including the maximum stiffness extends between C and D. The
outer periphery of the face extends from D to P.
[0058] Thus, there is a stiffness profile with varying stiffness
values corresponding to distances located radially outward from the
sweet spot toward the periphery of the face. The striking surface
of the face may be represented by quadrants defined by central axes
formed from a substantially vertical plane and a substantially
horizontal plane that each include the balance point of the face.
At least one stiffness profile is included in each quadrant,
extending generally radially from the balance point, and may or may
not coincide with one of the central axes.
[0059] While a particular stiffness profile found along any radial
line may or may not be repeated elsewhere on the face, each profile
preferably includes at least the minimum value at the greatest
radial distance from the sweet spot and the maximum value somewhere
between the minimum value and the sweet spot. A generally annular
region formed around the central region includes the maximum
stiffness values, which generally form an ellipse or circle or the
like, as well as stiffness values which are generally higher than
those found in either the central region or the outermost region of
the face. A preferred boundary stiffness value to differentiate
this annular region is at least about 3.5 times the minimum
stiffness values.
[0060] The total central region comprising all of the possible
stiffness profiles of the striking plate is in general reduced in
stiffness from the surrounding substantially annular region. The
local minimum stiffness point K found in the central region may
either be at the sweet spot and thus common to any profile taken,
or this point may be offset slightly and included only with a
specific stiffness profile, as shown in FIG. 10. Here two stiffness
profiles are shown and the length from BP to C1 is slightly less
than the length from BP to C2; the lengths D1 and D2 from BP may
differ, however both extend no more than about halfway to their
respective peripheral points P1 and P2.
[0061] The specific stiffness profiles, taken along any of the
radial lines from the sweet spot, are preferably gradual and
continuous, with each region delineated by the boundary values.
However, as formed using specific thicknesses, the desired
stiffness profiles may be achieved using, for example, constant
thickness values having abrupt changes between or within stiffness
regions, such as stepped and discontinuous sections. Or, the
thicknesses may include smoothly changing and continuous
thicknesses, such as chamfered sections. Also, the thicknesses may
include extremely variable thicknesses within a region that may be
observed as rough or sharp textured surfaces or softer, undulating
surfaces. Any combination of these types of thickness profiles may
be employed, as long as the resultant stiffness profiles are as
prescribed herein.
[0062] FIGS. 11-13 show a striking face 50 of the present invention
having an alternative thickness pattern. Thickness quadrants have
been formed and are divided by an X-shaped section 57 separating
individual quadrants (51, 52, 53, 54) that has the same thickness
as a periphery 55. This X-shaped section is centered at the balance
point 56. The separate regions of increased thickness shown as
quadrants (51, 52, 53, 54) are not symmetric about the balance
point, as shown in FIG. 12. The quadrant toward the left 52 has a
maximum thickness greater than the maximum thickness of the
quadrant toward the right 54 of the balance point.
[0063] The embodiments described in detail herein are merely
illustrative and the present invention may be readily embodied
using alternative materials, such as composites, in lieu of metals
or their alloys, as well as in hybrid constructions utilizing, for
example, laminations of metal and composite materials. The club
heads may be hollow or filled, have volumes greater than 300 cc or
less than about 250 cc, and may comprise unitary or multi-piece
bodies. In addition, the face portion may comprise an extension
over one or more of the junctions with the top, bottom, toe and
heel junctions with or without a hosel formation. Alternatively, it
may be desirable to form a substantially unitary head without a
separate striking plate, by casting or perhaps by the use of layers
of composite plies. In the present invention it is the striking
face region at the front of the club head having the specific
bending stiffness profiles that is significant.
[0064] Advantageously, the present invention is employed to achieve
COR values greater than about 0.80 across a greater portion of the
striking surface as compared to conventional club heads; e.g.,
substantially increasing the sweet spot for a so-called "hot" metal
wood golf club. However, the advantage of an increased sweet spot
of the present invention is also appreciated when applied to other
clubs, including utility-type club heads and irons.
[0065] Where the present invention is applied to an insert, the
separate striking plate may be forged or cast, or various welding
techniques may be employed to attach a separate portion behind a
constant thickness portion of the striking plate. With a welding
attachment of the face insert, a minimum thickness of the striking
plate at the periphery should still be present immediately adjacent
any weld bead formed. Alternatively, adhesive methods for
attachment of the striking plate may be used as known to those
skilled in the art. And, while the preferred constructions are
described in detail for metal woods, i.e., drivers and fairway
woods, it will be appreciated that the present invention may be
utilized in irons and other clubs.
[0066] In one preferred method of manufacturing the golf club head
of the present invention, a separate metallic striking plate is
produced using well known forging techniques to form the desired
bending stiffness profiles. Laser deposition is also contemplated,
wherein a laser device is used to melt a metallic material that is
then deposited onto a rear of the striking plate to obtain the
desired stiffness profile. Laser devices to perform this process
are known to those skilled in the art.
[0067] Yet another method provides the desired stiffness profile
via a structure formed on the rear of a striking plate by inertia
welding a separate piece to a front portion of the insert forming
the striking surface. FIGS. 14-16 show the rear portion of a
preferred striking plate in a sequence of configurations for
attachment. Specifically, FIGS. 14 and 14A show a disk 60
approximately 38 mm in diameter and approximately 3 mm in thickness
having a slightly convex surface formed on one side 61. FIGS. 15
and 15A show recesses or drive holes 62 formed around a periphery
63 of the disk, with the depths of the recesses limited by the
final thickness of the surface after attachment. A device (not
shown) for the inertia welding holds the disk at the recesses until
welding is completed. The final shaping of the rear of the striking
plate is achieved by machining, with a final preferred shape 65
shown in FIGS. 16 and 16A.
[0068] In any of the aforementioned methods, it may be desirable to
machine the rear surface of the striking plate as a final step.
Alternatively, a substantially constant thickness face may be
machined as the process to achieve the desired stiffness profiles,
instead of reserving the machining to a final step.
[0069] Composite materials may be used to form a striking plate
and/or to form the remainder of the club head. For the striking
plate, the desired stiffness profiles may be achieved within a
relatively constant thickness by utilizing appropriately positioned
materials, such as one or more types of metal fibers of varying
Young's Modulus with an epoxy resin. Alternatively, a surface
behind the striking surface of the face may be layered with
additional plies of composite material to achieve a variable
thickness profile. The additional plies may utilize the same or
different fibers from those forming the striking surface.
[0070] Another alternative embodiment of a golf club head 66 in
accordance with the present invention is depicted in FIG. 17. The
club head includes a hollow metallic body 68 and a striking plate
70. The body includes a heel portion 72, a toe portion 74, a sole
portion 76, and a crown portion 78 that cooperate to define an
opening sized to receive the striking plate. The striking plate is
shown in greater detail in FIGS. 18-19. The club head is normally
connected to a shaft (not shown) by a hosel 80 that is integrally
formed with the body. The club head preferably is manufactured such
that the body, including the heel portion, toe portion, sole
portion, crown portion, and hosel are integrally formed. The
striking plate, having a generally planar striking surface 82, is
fixedly attached by means known in the art. However, the various
portions of the preferred body may be separately molded, cast,
forged, electrochemically machined, or otherwise manufactured by
means known in the art, and fixedly attached to form the body.
[0071] Referring again to FIG. 17, the striking plate has the
generally planar striking surface on a front side, a rear surface
on a rear side, and a periphery for attachment at the opening on
the body. Each point on the striking surface has a thickness and
the striking surface has a total area. The striking plate has a
first thickness profile between the balance point and the top edge
86, a second thickness profile between the balance point and the
bottom edge 88, a third thickness profile between the balance point
and the first side edge 90, and a fourth thickness profile between
the balance point and the second side edge 92. The first, second,
third and fourth thickness profiles each have first, second and
third location with varying thickness values. The first and second
thickness profiles have thickness values at the second locations
that are less than the maximum values of the third and fourth
thickness profiles at the second locations but greater than minimum
values of the first, second, third, and fourth thickness profiles
at the first locations.
[0072] FIG. 18 is a detailed cross-sectional view of striking
plate, taken along lines 18-18 of FIG. 17. Referring to FIG. 18,
the first, second, third, and fourth thickness profiles of striking
plate all have thickness values at first locations 96 encompassing
the periphery of the striking plate and including minimum values
adjacent the edges. The first, second, third, and fourth thickness
profiles also all have thickness values at second locations 98
positioned between the first locations and the balance point 94.
The first and second thickness profiles have thickness values at
the second locations that are less than the maximum values of the
third and fourth thickness profiles at the second locations, but
greater than minimum values of the first, second, third, and fourth
thickness profiles at the first locations. The first, second,
third, and fourth thickness profiles have thickness values at the
third locations 100 in the central region that are less than the
maximum values of the third and fourth thickness profiles at the
second locations, but greater than the minimum values of the first,
second, third, and fourth thickness profiles at the first
locations.
[0073] The rear surface 84 of the striking plate includes an outer
rear surface 102 and an inner rear surface 104. A generally
ring-shaped raised surface 106 is formed between the outer surface
and the inner surface. Proximate the raised surfaces are an outer
shoulder 108 and an inner shoulder 110 that form transitions
between the raised surface and the respective outer surface and
inner surface. The raised surfaces and the outer and inner
shoulders cooperate to form a generally ring-shaped projection
extending rearward toward the inside of the club head cavity.
[0074] FIG. 19 is a detailed cross-sectional view of the striking
plate taken along lines 19-19 of FIG. 17. Referring to FIG. 19, the
third and fourth thickness profiles have thickness values that are
at least 1.5 times the minimum values and include points with the
maximum values at the second locations. The first, second, third,
and fourth thickness profiles have thickness values at the third
locations in the central region that are less than the maximum
values of the third and fourth thickness profiles at the second
locations, but greater than the minimum values of the first,
second, third, and fourth thickness profiles at the first
locations. The rear surface of the striking plate includes an outer
rear surface and an inner rear surface with a generally ring-shaped
raised surface defined between them. An outer shoulder and an inner
shoulder form transitions between the raised surfaces and the
respective outer surface and inner surface. The raised surface and
the shoulders cooperate to form a generally ring-shaped projection
extending rearward toward the inside of the club head cavity. The
maximum thickness values of the generally ring-shaped projection
occur at the second locations of the third and fourth thickness
profiles. This embodiment differs from earlier described
embodiments in that the maximum thickness values of the annular
projection occur only at the toe and heel portions of the striking
face and not at the sole and crown portions of the striking face.
This alternative embodiment provides the additional benefit of
having a high COR, while still providing significant forgiveness
for off center hits without the additional weight of having maximum
thickness values at the crown and sole portions of the annular
projection.
[0075] Another alternative embodiment of a golf club head in
accordance with the present invention includes a club head with a
hollow metallic body and a striking plate. The body includes a heel
portion, a toe portion, a sole portion, and a crown portion that
cooperate to define an opening sized to receive the striking plate.
The club head preferably is manufactured such that the body,
including the heel portion, toe portion, sole portion, crown
portion, and hosel are integrally formed. The striking plate,
having a generally planar striking surface, is fixedly attached by
means known in the art. However, the various portions of the
preferred body may be separately molded, cast, forged,
electrochemically machined, or otherwise manufactured by means
known in the art, and fixedly attached to form the body.
[0076] The striking plate has the generally planar striking surface
on a front side, a rear surface on a rear side, and a periphery for
attachment at the opening on the body. Each point on the striking
surface has a stiffness profile and the striking surface has a
total area. The striking plate has a first stiffness profile
between the balance point and the top edge, a second stiffness
profile between the balance point and the bottom edge, a third
stiffness profile between the balance point and the first side
edge, and a fourth stiffness profile between the balance point and
the second side edge. The first, second, third, and fourth
stiffness profiles of striking plate all have stiffness values at
first locations encompassing the periphery of the striking plate
and including minimum values adjacent the periphery. The first and
second stiffness profiles have stiffness values at the second
locations that are less than the maximum values of the third and
fourth stiffness profiles at the second locations, but greater than
minimum values of the first, second, third, and fourth stiffness
profiles at the first locations. The first, second, third, and
fourth stiffness profiles have stiffness values at the third
locations in the central region that are less than the maximum
values of the third and fourth stiffness profiles at the second
locations, but greater than the minimum values of the first,
second, third, and fourth stiffness profiles at the first
locations.
[0077] The third and fourth stiffness profiles have stiffness
values that are at least 3.5 times the minimum stiffness values and
include points with the maximum values at the second locations. The
first, second, third, and fourth stiffness profiles have stiffness
values at the third locations in the central region that are less
than the maximum values of the third and fourth stiffness profiles
at the second locations, but greater than the minimum stiffness
values of the first, second, third, and fourth stiffness profiles
at the first locations. The maximum stiffness values of the
striking plate occur at the second locations of the third and
fourth stiffness profiles.
[0078] It should be evident from the drawings and the discussion
above that the golf club head of the present invention exhibits
greater forgiveness across a substantial portion of the striking
surface while continuing to impart high initial velocity to a golf
ball.
[0079] Although the invention has been described in detail with
reference to the presently preferred embodiments, those of ordinary
skill in the art will appreciate that various modifications can be
made without departing from the invention. Accordingly, the
invention is defined only by the following claims.
* * * * *